1. Field of the Invention
The present invention relates to an optical disk apparatus for optically performing playback from a disk or recording on and playback from the disk, and particularly to an optical disk apparatus for performing a track jump and a focus jump necessary to effect an interlayer Jump on a disk having a plurality of recording layers.
2. Description of the Related Art
In an optical disk such as a compact disk (hereinafter called a “CD”), a digital versatile disk (hereinafter called a “DVD”), focus control or tracking control has been performed which allows a laser spot to follow a recording layer or a recording track with high accuracy in order to accurately read and write information recorded on the optical disk.
With the increasing operational speed of recent CD and DVD, however, the influence of axial and radial deviations becomes large so that an accurate follow-up to the recording layer or recording track is becoming difficult. Therefore, information indicative of a relationship in position between an optical detecting means for data reading and an optical disk is stored in advance which acts as an axial run-out component or a radial run-out component, and thereafter the information is added to a drive signal of an optical pickup as a feedforward signal, thereby enabling high-accuracy focus control and tracking control (see Japanese Published Unexamined Patent Application No. Hei 8(1996)-161840, for example).
In order to read information from a desired track, a focus jump or track jump for moving a laser spot between recording layers or tracks is carried out. However, it becomes difficult to perform a stable jump operation with the speeding-up of rotation of a disk. Thus, in order to solve this problem, a stored axial deviation component or radial deviation component is added to a jump signal to thereby enable a stable jump operation (see Japanese Published Unexamined Patent Application No. 2000-20967, for example).
The above-described two known arts respectively have such a configuration that the axial run-out component or radial run-out component of the optical disk is stored in its corresponding memory and added to a servo drive signal as needed. It is therefore preferable that when these two known arts are applied simultaneously, the memory is used in common in terms of a cost reduction.
A configuration example in this case will next be described. Incidentally, since a focus system and a tracking system can make use of a similar configuration respectively, the tracking system will be explained in the following description.
FIG. 2 is a block diagram showing an optical disk apparatus using the conventional system referred to above. Reference numeral 1 denotes an optical disk, reference numeral 2 denotes an objective lens, reference numeral 3 denotes an optical pickup, reference numeral 4 denotes a signal processor, reference numeral 5 denotes an AD (Analog/Digital) converter. Reference numeral 6 denotes a tracking controller, reference numeral 7 denotes a spindle motor, reference numeral 8 denotes a rotation detection signal generator, reference numeral 9 denotes a rotational position detector, and reference numeral 10 denotes a radial deviation component detector. Reference numeral 11 denotes a jump signal generator, reference numerals 12 and 13 denote switches, reference numeral 14 denotes an adder, reference numeral 15 denotes a DA (Digital/Analog) converter. Reference numeral 16 denotes a driver circuit, reference numeral 17 denotes a CPU (Central Processing Unit), reference numeral 18 denotes a thread controller, reference numeral 19 denotes a driver circuit, reference numeral 20 denotes a thread motor. Reference numeral 21 denotes an optical pickup feed mechanism.
In the drawing, the optical disk 1 is irradiated with laser light to perform reading, erasure and writing of information. A laser light source (not shown) and a light rece 1 vlng device (not shown) are built in the optical pickup 3 used as optical detecting means. Also the optical pickup 3 is provided with the objective lens 2. Laser light emitted from the laser light source is applied to the optical disk 1 via the objective lens 2. At this time, the laser light is gathered by the objective lens 2, which in turn is focused on a desired recording layer or a recording track of the optical disk 1. In the case of the information reading, the light reflected from the optical disk 1 is received by the optical pickup 3 through the objective lens 2, where it is converted into an electric signal. The electric signal is supplied to the signal processor 4.
Also an actuator (not shown) 1S built in the optical pickup 3 and moves the objective lens 2 in a substantially radial direction of the optical disk 1 in accordance with a drive signal outputted from the driver circuit 16 (incidentally, it moves the objective lens 2 in the direction of thickness of the optical disk 1 in the case of the focus system).
A signal outputted from the optical pickup 3 is processed in the signal processor 4 where a tracking error signal TE corresponding to a deviation from a track on a spot of the laser light irradiated onto the optical disk 1 is generated. Thus, the tracking error signal TE is information indicative of the relationship of position between the optical detecting means and the optical disk 1. The information is converted into digital data by the AD converter 5 at a predetermined sampling period, followed by supply to the tracking controller 6 where it is subjected to a process of compensation for gain and each phase necessary to improve stability and followability of a tracking servo, after which it is outputted as a tracking control signal TC. The tracking control signal TC is supplied to the adder 14 via the switch 12 and even to the radial deviation component detector 10.
The spindle motor 7 rotates the optical disk 1 and outputs a signal synchronized with its rotation. The output signal of the spindle motor 7 is supplied to the rotation detection signal generator 8 where it is processed, after which the processed signal is outputted as a disk motor FG (frequency generation) signal synchronized with the rotation of the optical disk 1. The disk motor FG signal is supplied to the rotational position detector 9 where it is processed, so that a rotational position detection signal RP indicative of the absolute phase of the rotating optical disk 1 is generated. In the radial deviation component detector 1a, a radial deviation component EC used as an AC (Alternating Current) component caused by a radial deviation of the optical disk I, which is contained in the tracking control signal TC, is detected over a period corresponding to one rotation of the optical disk 1, on the basis of the rotational position detection signal RP, and then stored and held therein. This is repeatedly read and outputted. Accordingly, the radial deviation component EC represents a change in the position relationship between the optical detecting means and the optical disk 1 due to the radial deviation (axial deviation in the focus system). The radial deviation component EC is supplied to the adder 14 via the switch 13.
When a jump signal JS outputted from the CPU 17 is “L” (low level), the jump signal generator 11 outputs a jump pulse signal JP of “0”. When the jump signal JS is “H” (high level), the jump signal generator 11 outputs a jump pulse signal JP of “1” or “−1” in accordance with acceleration or deceleration.
The switches 12 and 13 respectively perform ON (close) and OFF (open) operations according to control signals SC1 and SC2 outputted from the CPU 17. Assume that in the following description, when the control signals SC1 and SC2 are “L”, the switches 12 and 13 are turned OFF, whereas when the control signals SC1 and SC2 are “H”, the switches 12 and 13 are turned ON.
The adder 14 adds the jump pulse signal JP outputted from the jump signal generator 11, the tracking control signal TC supplied from the tracking controller 6 via the switch 12, and the radial deviation component EC supplied from the radial deviation component detector 10 via the switch 13. Digital added data outputted from the adder 14 is converted into an analog signal by the DA converter 15 at a predetermined period. Incidentally, the conversion periods of the AD converter 5 and the DA converter 15 are regarded to be the same here. The output signal of the DA converter 15 is amplified by the driver circuit 16, which in turn is supplied to the tracking actuator in the optical pickup 3 as its drive signal. In accordance with the drive signal, the objective lens 2 changes in its position in the radial direction of the disk 1.
The CPU 17 outputs an enable signal WR for the radial deviation component detector 1a, a jump signal JS for controlling the jump signal generator II, and control signals SC1 and SC2 for turning the switches 12 and 13 ON and OFF respectively.
The output signal of the adder 14 is supplied to the thread controller 18 where the gain for improving followability of a thread servo is compensated. Incidentally, the thread controller 18 controls the position of the optical pickup 3 in such a manner that the objective lens 2 moved by the tracking actuator in the optical pickup 3 does not exceed its travelling limit. A signal outputted from the thread controller 18 is amplified by the driver circuit 19, followed by being supplied to the thread motor 20 as a drive signal. Thus, the thread motor 20 drives the optical pickup feed mechanism 21 to move the optical pickup 3 in an inner peripheral or outer peripheral direction of the optical disk 1.
The operation of the optical disk apparatus having the above configuration will next be explained using FIGS. 2, 3 and 4.
FIGS. 3 and 4 are respectively waveform diagrams showing signals at the respective portions in FIG. 2.
Referring to FIG. 3, until a time t1 that elapses since the start of the rotation of the optical disk I, the jump signal JS outputted from the CPU 17 is set to “L”, the control signal SCI for the switch 12 is set to “H”, and the control signal SC2 for the switch 13 is set to “L”, respectively. At this time, the jump signal generator 11 has already outputted the jump pulse signal JP of “0” (that is, no jump pulse signal JP is outputted). Further, the switch 12 is held ON, and the switch 13 is held OFF. Therefore, the tracking servo becomes a closed loop so that tracking control is performed on a steady basis. Further, the CPU 17 has already supplied the enable signal WR of “L” to the radial deviation component detector 10 (that is, no enable signal WR is not supplied to the radial deviation component detector 10). Thus, the radial deviation component detector 10 does not perform the operation of detecting the radial deviation component EC.
FIG. 3 line (a) shows the tracking error signal TE outputted from the signal processor 4. Since tracking suppression gain is not sufficient, a component synchronized with a period equivalent to one rotation of the optical disk 1 appears.
FIG. 3 line (b) shows the tracking control signal TC outputted from the tracking controller 6. The tracking control signal TC is one obtained by compensating for the gain and phase of the tracking error signal TE. The tracking control signal TC is digital data but expressed in analog form for convenience.
Here, FIG. 4 line (a) shows the disk motor FG signal outputted from the rotation detection signal generator 8. Assume here that the disk motor FG signal is generated with 6 periods or cycles per rotation of the optical disk 1. FIG. 4 line (b) shows a rotation synchronizing signal ROT generated by the rotational position detector 9, which is one synchronized every 6 cycles of the disk motor FG signal shown in FIG. 4 line (a).
Further, the rotational position detector 9 outputs a multiplication signal obtained by effecting a multiplication on the disk motor FG signal, which is shown in FIG. 4 line (c). Assume that the rotational position detector 9 measures a period T1 of the disk motor FG signal and outputs, twice, signals each having a time T 1/2 equivalent to one-half the measured period T1 as a period as viewed from the next period of the disk motor FG signal, thereby generating the multiplication signal shown in FIG. 4 line (c) in which the frequency of the disk motor FG signal is set twice. Further, the rotational position detector 9 has a counter which is reset in response to the rotation synchronizing signal ROT and counts up at both edges of the multiplication signal. A value counted by the counter is outputted as a rotational position detection signal RP. FIG. 4 line (d) shows the rotational position detection signal RP. The counted value changes from 0 to 23 during a period of one rotation of the optical disk 1. Such counted values represent sequential positions (phases) for each round on the optical disk 1.
As shown in FIG. 3 line (c), the CPU 17 set the enable signal WR to “H” during a period of a time t1 to a time t2. Thus, the radial deviation component detector 10 is operated with a memory built therein being set as write enable. The radial deviation component detector 10 set the rotational position detection signal RP supplied from the rotational position detector 9 as address data for the memory, and extracts a radial deviation component EC of the optical disk 1 from the tracking signal TC supplied from the tracking controller 6 and stores it. This is repeatedly read and outputted.
The operation of the radial deviation component detector 10 will now be explained.
FIG. 5 is a block diagram showing a configuration example of the radial deviation component detector 10. Reference numeral 10a denotes a BPF (BandPass Filter), and reference numeral 10b denotes a memory. Portions associated with those shown in FIG. 2 are respectively identified by the same reference numerals, and the description of certain common ones will therefore be omitted.
In the same drawing, the radial deviation component detector 10 comprises the BPF 10a and the memory 10b. The center frequency of the BPF 10a is set to a rotational frequency (frequency of a radial deviation) of the optical disk 1 (FIG. 2). The radial deviation component detector 10 extracts a radial deviation component caused by the radial deviation of the optical disk 1 at the tracking control signal TC (FIG. 3 line (b)). The memory 10b is in a write enable state (write state). However, a read state is allowed) by the enable signal WR of “H” during the period of the times t1 to t2 (FIG. 3). A signal outputted from the BPF 10a is set as input data, and a rotational position detection signal RP outputted from a rotational position detector 9 is set as address data, whereby the writing of the input data is performed. As shown in FIG. 4 line (d), the rotational position detection signal RP is one in which the value changes from 0 to 23 during one rotation period of the disk 1 and which represents the sequential rotational phases of the optical disk 1. Therefore, the memory 10b stores the tracking control signal TC (i.e., radial deviation component) supplied via the BPF 10a under the sequential rotational phases of the optical disk 1. The period between the times t1 and t2 in which the enable signal WR shown in FIG. 3 line (c) is “H”, is a period during which the radial deviation component extracted at the BPF 10a is written into the memory 10b. The period is set to more than or equal to one rotation period of the optical disk 1. Thus, the radial deviation component corresponding to one rotation period of the optical disk 1 is stored in the memory 10b. 
The recorded radial deviation component is immediately read from the memory 10b and outputted from the radial deviation component detector 10 as a radial deviation component EC. FIG. 3 line (d) shows the radial deviation component EC outputted from the memory 10b. When the enable signal WR reaches “L”, the memory 10b completes its write operation and performs its reading alone. Thus, the radial deviation component corresponding to one rotation period of the optical disk 1 is repeatedly read from the memory 10b in sync with the rotation of the optical disk I, which is outputted from the radial deviation component detector 10 as the radial deviation component EC. Incidentally, the memory 10b may be a memory wherein after the completion of recording of the radial deviation component corresponding to one rotation period of the optical disk I, its reading is started.
FIG. 6 is a block diagram showing another example of the radial deviation component detector 10. Reference numeral 10c denotes an LPF (Lowpass Filter), reference numeral 10d denotes a memory, reference numeral 10e denotes an average arithmetic circuit, and reference numeral 10f denotes a subtractor. Portions associated with those shown in FIG. 2 are respectively identified by the same reference numerals, and the description of certain common ones will therefore be omitted.
In the same drawing, the radial deviation component detector 10 comprises the LPF 10c, the memory 10d, the average arithmetic circuit 10e, and the subtractor 10f. The cut-off frequency of the LPF 10c is set to about several times to ten times the rotational frequency of the optical disk 1. The radial deviation component detector 10 extracts a wave obtained by combining a radial deviation component contained in a tracking control signal TC and its harmonic component together. Since the radial deviation component is not a monotonous sin wave in most cases, there is a possibility that the radial deviation component detector will be able to detect the radial deviation component faithfully as compared with the radial deviation component detector 10 having the configuration shown in FIG. 5. The memory 10d operates in a manner similar to the memory 10b shown in FIG. 5 (thus, the present memory 10d may be such a memory that after the completion of recording of the radial deviation component corresponding to one rotation period of the optical disk 1, its reading is started). During a period in which an enable signal WR is “H”, a rotational position detection signal RP Js set as address data, and a signal outputted from the LPF 10c is stored and repeatedly outputted. The output signal of the memory 10d is averaged by the average arithmetic circuit 10e, so that a DC (Direct Current) offset (i.e., DC component) caused by the position relationship between the objective lens 2 and the optical pickup 3 is extracted. The output signal of the memory 10d is subtracted from the output signal of the average arithmetic circuit 10e by the subtractor 10f, so that the DC offset is eliminated to obtain a radial deviation component EC composed of an AC (Alternating Current) component. The radial deviation component EC is supplied to the switch 13 (FIG. 2).
Incidentally, since the center frequency of the BPF 10a is set to the rotational frequency of the disk 1 in the radial deviation component detector 10 shown in FIG. 5, the DC component is sufficiently attenuated with respect to the output signal thereof.
Referring to FIGS. 2 and 3, at the time t3 after the enable signal WR is set to “L”, the CPU 17 brings the control signal SC2 to “H” to turn ON the switch 13 as shown in FIG. 3 line (e). Thus, the radial deviation component EC outputted from the radial deviation component detector 10 is supplied to the adder 14 via the switch 13 where it is added to the tracking control signal TC outputted from the tracking controller 6. FIG. 3 line (f) shows a radial deviation component EC outputted through the switch 13.
The radial deviation component EC outputted through the switch 13 is an AC component and changes the position of the objective lens 2 as a feedforward signal. Namely, the radial deviation component is stored in the radial deviation component detector 10 (FIGS. 5 and 6) and applied to a tracking servo loop as a feedforward signal, thereby making it possible to suppress the AC component caused by the radial deviation of the optical disk 1. Since, at this time, the feedback loop of the tracking system suppresses the remaining DC component caused by the radial deviation, the tracking error signal TE (FIG. 3 line (a)) and the tracking control signal TC (FIG. 3 line (b)) respectively change with the DC component caused by the radial deviation as a main component after the time t3. Further, since the DC gain of the tracking servo loop is high like about 60 dB to about 80 dB, the DC component can be sufficiently suppressed.
FIG. 7 is a waveform diagram showing signals at the respective portions of FIG. 2 where a track jump is preformed from the state in which as described above, the radial deviation component is stored and applied to the tracking servo loop as the feedforward signal, wherein FIG. 7 line (a) shows a tracking error signal TE, FIG. 7 line (b) illustrates a control signal SC1 of the switch 12, FIG. 7 line (c) depicts a jump signal JS, FIG. 7 line (d) shows a jump pulse signal JP, FIG. 7 line (e) illustrates an output signal (radial deviation component EC) of the switch 13, and FIG. 7 line (f) depicts a signal outputted from the DA converter IS, respectively.
In FIG. 7, there exists a continuation from the time t3 of FIG. 3 till a time t4, and the tracking control is being performed. During a track jump period between the time t4 and a time t5, the CPU 17 brings the control signal SC1 to “L” to turn OFF the switch 12. In doing so, the tracking loop is brought to an open state so that the tracking control is not performed. Also the CPU 17 brings the jump signal JS to “R” during the track jump period between the times t4 and t5. Thus, as shown in FIG. 7 line (d), the jump signal generator 11 generates an accelerating pulse necessary to allow an optical spot to jump to an adjacent track on the optical disk 1. Then the jump signal generator 11 generates a jump pulse signal JP consisting of the accelerating pulse and a decelerating pulse for pulling back the optical spot accelerated by the accelerating pulse in such a manner that the optical spot does not jump over the adjacent track and overreach it, and outputs it therefrom. The jump pulse signal JP is added to the radial deviation component EC outputted through the switch 13 by the adder 14, the added result of which is supplied to the thread controller 18 and the DA converter 15. Thus, during the track jump period between the times t4 and t5, as shown in FIG. 7 line (f), the output signal of the DA converter 15 results In a signal obtained by adding accelerating and decelerating voltages of the jump pulse signal JP to the radial deviation component EC of the optical disk I, which is indicated with a dotted line. Therefore, the optical disk 1 enables a stable track jump without being affected by its radial deviation.